Autoclaving Effectively Sterilizes Contaminated Retained Cement in Orthopaedic Surgical Trays.

BACKGROUND

Retained polymethylmethacrylate (PMMA) in surgical instrument trays and on instruments is becoming more common and is a disquieting situation for the arthroplasty operating room team. Although retained debris may be sterile after autoclaving, previous studies have not specifically investigated bacterial viability on retained PMMA. This study determined whether heavily contaminated PMMA surfaces and instruments covered in PMMA could be effectively sterilized by clinically utilized autoclaving protocols.

METHODS

Mature methicillin-susceptible Staphylococcus aureus (MSSA) and Escherichia coli biofilms were grown on PMMA coupons with a smooth surface (n = 5 per condition) or with deep crevices (n = 5 per condition) and on threaded screws, which were inserted into polymerizing PMMA (n = 5 per condition). PMMA coupons and PMMA-covered screws were subjected to 3 autoclave sterilization protocols. Colony-forming unit (CFU) counts and adenosine triphosphate (ATP) levels were measured to detect viable bacteria. Scanning electron microscope (SEM) images were obtained to determine whether biofilm was present.

RESULTS

Non-autoclaved PMMA surfaces were heavily contaminated, with values of 4.1 ± 2.3 × 10 6 CFUs/mL for S . aureus and 2.4 ± 1.2 × 10 6 CFUs/mL for E . coli. ATP levels of 3,230 ± 1,297 relative light units (RLU) for S . aureus and 1,006 ± 602 RLU for E . coli were observed. Crevices and screws were also heavily contaminated. Following autoclaving, CFUs/mL counts of <10 and RLU levels of <5 (beneath the hygienic threshold for cleanliness) were recorded on all PMMA surfaces, crevices, and screws. SEM confirmed that the biofilm structures remained intact, but they did not contain viable bacteria.

CONCLUSIONS

PMMA and PMMA-covered instruments contaminated with gram-positive or gram-negative biofilms are effectively sterilized using clinical autoclaving protocols.

CLINICAL RELEVANCE: Retained PMMA and PMMA-covered surgical instruments that undergo a clinical autoclaving protocol do not carry viable bacteria.